This paper reviews the current knowledge on the toxicity, speciation and biogeochemistry of arsenic in aquatic
environmental systems. The toxicity of arsenic is highly dependent on the chemical speciation. The effects of
pH, Eh, adsorbing surfaces, biological mediation, organic matter, and key inorganic substances such as sulfide
and phosphate combine in a complex and interwoven dynamic fashion to produce unique assemblages of
arsenic species. The number of different arsenic species found in environmental samples and an understanding
of the transformations between arsenic species has increased over the past few decades as a result of new and
refined analytical methods. Changes in arsenic speciation and in total arsenic content of foods upon processing
have suggested possible risks associated with processed and unprocessed food. Arsenic removal from water
using adsorbents, chemical oxidation, photolysis and photocatalytic oxidation techniques is also reviewed